"Several of the concerns about Oracle's acquisition of Sun have revolved around how Unix technologies led by Sun would continue under the new ownership. As it turns out, Solaris users might not have much to worry about, as Oracle executives on Wednesday affirmed their commitment to preserving the efforts. In the case of Solaris, Oracle had already been a big supporter of the rival Linux operating system. Oracle has its own Enterprise Linux offering, based on Red Hat Enterprise Linux. For Oracle CEO Larry Ellison, the idea that Linux and Solaris are mutually exclusive is a false choice."

Thing is, UNIX is no where near stable and secure enough for the Mainframe. UNIX like AIX and Solaris are great for big iron and the odd mainframe LPAR (which will be perfectly happy to run Linux too) but if IBM swapped zOS out for AIX on all of it's mainframes and started using a virtualized environment to run all the then legacy MVS code, their customers would A) Throw a hissy fit and B) Probably sue them.

Mainframes are the most closed environment in computing and although I dislike MS and Apple's way of doing business, they both pale in comparison to IBM and the Mainframe. Every one of those machines are hooked up to an external phone line that will phone home the minute you reach 91% CPU usage. What happens is the reserve CPUs will kick in and you will be billed for the added system usage and let me tell you, the renting of a mainframe is not cheap.

But all in all, the hardware costs are nothing compared to the price of software on zOS. This is why you now see zLinux and IBM wanting to port Solaris over. It's a win/win for them as first off, customers want to be able to run a fully supported, cheap open source stack in a sandboxed environment and secondly, it means more people will find the Mainframe more attractive and flexible. For example, the cost of Websphere for zOS is something like 100 times that of Webspere for linux. With Thomcat on zLinux, you pay for the support.

In the end though, if the underlying MVS system, with it's almost bullet proof security and total reliability, where no longer present, the mainframe would lose it's biggest selling points.